Convection drier with a travelling bed

ABSTRACT

A convection drier with a travelling bed is provided for drying and heating bulk materials such as coal, quick coke, blast furnace slag etc. The fundamental principle of its operation consists in blowing through a layer of dried material which is continuously travelling. A stream of a drying agent/hot air or combustion gases/ is passed through a bed of dried material blowing upon the particular particles of this material and removing moisture therefrom. Owing to the fact that the drying agent is passed in variable directions, a good turbulence of air flow as well as a high heat exchange can be obtained. The dried bed is passed between two perforated walls by means of a chain conveyor or falls sliding down by itself due to the force of gravity. The overall dimensions of the drier of the invention are far smaller than those ones of conventional driers. The drier can be adapted to drying bulk materials in large quantities and requires only small power supplies. The gas/even polluted combustion gases/ used in the drying process is preliminary cleaned in the drier for further use.

United States Patent Pikon et al.

[ Apr. 16, 1974 CONVECTION DRIER WITH A TRAVELLING BED [76] Inventors: Jerzy Pikon, Aleja onajowa 14/27;

Piotr Wasilewski, Karolinki Str. 25, both of Gliwice; Boleslaw Mitka, Swidnicka Str. 38/17, Katowice-Ligota, all of Poland [22] Filed: Feb. 28, 1973 [21] Appl. No.: 336,761

[30] Foreign Application Priority Data Mar. 6, 1972 Poland 153878 Apr. 20, 1972 Poland 154865 May 30, 1972 Poland 155683 [52] U.S. Cl 34/203, 34/172, 34/190 [51] Int. Cl. F26b 19/00 58] Field of Search 34/102, 172-176, 34/184-190, 201-208, 236; 198/75, 76, 84

[5 6] References Cited UNITED STATES PATENTS 1,880,284 10/1932 Schenk 34/172 FOREIGN PATENTS OR APPLICATIONS 501,063 2/l95l Belgium .1 34/90 806,111 3/1951 Germany 34/206 Primary Examiner-John J. Camby Assistant Examiner.lames C. Yeung Attorney, Agent, or Firm-Eric H. Waters 5 7] ABSTRACT A convection drier with a travelling bed is provided for drying and heating bulk materials such as coal, quick coke, blast furnace slag etc. The fundamental principle of its operation consists in blowing through a layer of dried material which is continuously travelling. A stream of a drying agent/hot air or combustion gases/ is passed through a bed of dried material blowing upon the particular particles of this material and removing moisture therefrom. Owing to the fact that the drying agent is passed in variable directions, a good turbulence of air flow as well as a high heat exchange can be obtained. The dried bed is passed be-v tween two perforated walls by means of a chain conveyor or falls sliding down by itself due to the force of gravity. The overall dimensions of the drier of the invention are far smaller than those ones of conventional driers. The drier can be adapted to drying bulk materials in large quantities and requires only small power supplies. The gas/even polluted combustiongases/ used in the drying process is preliminary cleaned in the drier for further use.

6 Claims, 3 Drawing Figures PATENTEDAPR 16 974 SHEET 2 OF 3 CONVECTION DRIER WITH A TRAVELLING BED The invention relates to a convection drier with a travelling bed for drying bulk materials.

In the hitherto known convection driers for drying bulk materials the drying agent flows above the surface of dried material as exemplary in the drum or tray driers or the drying agent entrains the particles of dried material as in the pneumatic or fluidized solids driers.

In the both cases considerable excess of the drying agent is used what appears unpractical because of low heat utilization and furthermore great quantities of dried materials are'carried away from driers what neccssitates to use dust collectors of various types preventing from high losses of dried material.

It is an object of the invention to construct an improved convection drier with a travelling bed for drying bulk materials, which is devoid of previous disadvantages and characterized by the simplified construction providing increased yields and requiring reduced supplies of drying heat. v

This problem was solved by providing the drier with two parallel perforated confined walls'and with a conveyor disposed between said walls and having shelves suspended on chains, and the said conveyor is guided so as to form a chamber in'the middle of the drier wherein the drying agent is supplied. In the upper and bottom part of the drier on horizontal segments are stub pipes serving for loading and unloading dried material. The travelling rate of dried material is dependent upon the drying time and may be optionally adjusted by changing the number of revolutions of the drive wheel according to the desired humidity of the final material. The drier according to the invention has a simple construction which enables to carry out the drying process continuously. Owing to the fact that the drying agent is flowing throughout the bed of dried material the heat utilization and the drying rate are far higher than in the driers where the drying agent is passed above the surface of material provided for drying. Application of perforated walls in form of wire gauzes or perforated plates unables the particles of dried material to be carried away with the drying agent, thus providing facili ties for convection drying without necessity to use dust collectors. Furthermore, the drier may be air heated or with polluted exhaust gases, owing to location of the chamber in the central part of the drier where exhaust gases can be partially dedusted and the residual dust settles on the layer of the dried material. The exhaust gases leaving the drier are dedusted and their heat is utilized in far higher degree than in the known driers. Generally as the resistances of flow in the drier according to the invention do not exceed the resistances in the known dust collectors such as cyclones and multicyclones, so the drier of the invention enables'waste heat of polluted exhaust gases to be utilized and thus the drier is not only adapted to drying but also to dedusting exhaust gases on the layer of the dried bed.

The drier of the invention can be applied in a wide scope particularly for drying bulk materials such as coal, fine coal, coke, brown coal, sand, corn and ethers. As indicated above it can be also used for utilizing waste heat of exhaust gases from steam boilers etc. In order to enable sizing and oiling operations the drier may be provided with means for additional size distribution of dried material and oiling and ramming means preventing from forming channels in the dried material.

In this variant of the drier the outlet stub pipes are connected with cascade sieves, which are provided with outlet means for withdrawing coarse and fine grained material. The oil sprayers are placed under sieves and near feed stub pipes on horizontal segments of the chamber are ramming means in form of pistons or rollers. The condensers for condensing gases and recovering the condensate can be also connected to outlet stub'pipes in order to withdraw the drying agent. The drier can be also blown through as well on vertical as on horizontal segments. Owing to possibility of fractionating and oiling the material ,in the drier, the drier of the invention can be especially adapted to coking processes for low-grade, slow-coking coals, for manu-.

facturing low carbonization coke or for drying and heating the coking charges.

The ramming means in form of pistons or rollers prevent from forming channels in the dried material and provide for shortening the drying period.

.In another variant of the drier the conveyor or conveyors with shelves form a triangle with the vertex headed downwards and are placed in a confined chamher or chambers. In the upper part of the drier are feed stub pipes and outlet stub pipes in the bottom part. The conveyors may be provided with a common drive.

In thec'ase when the material is loose and easy flowing the drier has no conveyors but only :outlet stub pipes provided with batchers. Thus the construction of the drier is considerably simplified. This technical solution makes possible to feed the material from above and withdraw it in the bottom part of the drier, so the drier can be much easier loaded and unloaded.

Furthermore the downward motion of the dried material enables good filling of the drierwithout necessity to use additional ramming means such as pistons or rollers and provides the uniform air distribution on the wholesurface'of thedrying wall. Application of two separate conveyors and two chambers enables two various materials to be driedand in the event of failure the drier can be cut off by half. It will be also noted that when materials are easyfalling down between two perforated walls the conveyors and the power transmission system can be eliminated. The drier may be also used for heating the cokingcharge.

The drier according to the inventionisexemplary shown in the accompanying drawing, where FIG. 1 presents the vertical section,

FIG. 2 a variant of the drier furnished with sieves for fractionating materials, condensers for steam condensation and ramming means and FIG. 3 presents a variant of the drier wherein the material is falling downwards. In this last variant when materials provided for drying are loose and easy flowing the chain drive system may be eliminated and the drier equipped only with batchers in its bottom part.

The bed 1 comprising a dried material is conveyed between two perforated walls 2 and 3 by means of chain conveyor 4 equipped with shelves 5. The whole system is driven through a sprocket wheel 6 by an electric motor provided with a reduction gear. The drier is continuously filled with materials on the horizontal segments by stub pipes 7 and also on the horizontal segments the dried materials are unloaded'by stub pipes 8.

A drying agent in form of hot air or exhaust gases is continuously fed on vertical segments of the drier throughout the bed of dried material I. Thebed 1 after being introduced into a drier by stub pipes 7 is conveyed by means of shelves of conveyor 4.

On vertical segments of the drier the hot drying agen flows through the layer of the bed 1 and causes its drying. The dried bed is withdrawn by stub pipes 8. The rate of travelling of the dried material depends upon the rate of drying and is adjusted by changing number of revolutions of drive wheels 6. Hot air or exhaust gases are fed to the chamber 10 by stub pipe 9. If exhaust gases are polluted they will be partially dedusted in the chamber 10 as the dust particles fall on the bottom of the drier whcrefrom they are collected by the conveyor 4 which is open from inside of the chamber.

The exhaust gases are further purified on the layer of the dried bed 1. The cold and moist air leaves the drier by stub pipe 11. In the variant of the drier the bed 1 of dried material is rammed by pistons 21. Stub pipes 8 are provided with cascade sieves 12 which enable the material to be distributed into different fractions. The

fine material is withdrawn by the stub pipe 14 and directed to further processing, and corse fractions are taken off by stub pipes 13 to milling. Under sieves 12 the sprayers 15 may be alternatively installed in order to oil the fractionated material. The drying agent leaves the drier by the steam outlet pipes 11 to which the condensers 16 for steam condensation and recovering of condensate can be adjoined. The condensate is withdrawn from the condenser 16 by stub pipe 18. Uncondensed gases escape to atmosphere by stub pipes 17. The cooling agent in form of air or water is fed by stub pipes 19 and withdrawn by stub pipes 20.

I In another variant of the drier the bed 1 is conveyed by means of two conveyors 4 provided with shelves 5. The whole system is driven by toothed wheels 6 which are connected through a reduction gear with an electric motor. These two conveyors may be driven by a common drive or by" separate drives. The drier is continuously filled in the upper part by stub pipes 7 and'unloaded in its bottom part by stub pipes 8. The drying agent comprising hot air, exhaust gases or superheated steam is fed by stub pipe 9 and passed through thebed of dried material on the vertical segments of the drier. The bed 1 comprising material provided for drying is introduced to the drier by stub pipes 7 and conveyed downhill by means of shelves 5 of the conveyor 4. In the vertical segments of the drier the hot drying agent flows throughout the layer of material provided for drying and causes its drying. The dried bed 1 is withdrawn by stub pipes 8. The travelling rate of the dried bed depends upon the drying rate and is adjusted by changing number of revolutions of drive wheels 6. When the material provided for drying is loose and easy flowing it falls by itself between two perforated walls 2 and 3 and in this case the conveyor 4 may be eliminated with regard to flow of the material under force of gravitation and only stub pipes should be provided with batchers 23. Hot air or exhaust gases are fed by stub pipes 9 to two chambers 10 formed by a partition wall 22. Exhaust gases are preliminary de-dusted in chambers 10 wherein dust particles fall down on the bottom. Further scavenging of exhaust gases occurs on the layer of the dried bed 1. After passing through the bed 1 cold and moist air escapes to atmosphere or it is withdrawn by stub pipes which is not shown in the drawing.

What we claim is:

1. A convection dryer'with a travelling bed, comprising; a pair of parallel spaced perforated walls; a movable conveyor extending between said walls in generally vertically and horizontally paths of movement; said conveyor including shelves and chain meansinterconnecting said shelves so as to define an enclosed chamber encompassed by said conveyor and said walls; inlet means for supplying wet materials to horizontal portions of said conveyor; outlet means for removing dried materials from horizontal portions of said conveyor; inlet means for supplying a gaseous drying medium into said enclosed chamber; and outlet means for withdrawing said drying medium, said inlet and outlet means for said gaseous drying medium being positioned so as to effect flow of said drying medium through said materi als in at least the vertical portions of said movable conveyor.

2. A dryer according to claim 1; comprising cascade sieve means being positioned in the outlet means for said dried materials, said cascade sieve means including outlets for withdrawing respectively fine and coarse fractions of said materials; oil spray means connected to at least one of said last-mentioned outlets; and ramming means positioned at the horizontal portions of said conveyor proximate said inlet means for said wet materials and being adapted to compact said materials.

3. A dryer according to claim 1, comprising a pair of said conveyors each having triangular paths of movement'including a vertical and an upper horizontal portion; inlet means for said wet materials communicating with the upper horizontal portions of each of said conveyors; and outlet means for said dried materials being located proximate the lower ends of said conveyors.

4. A dryer according to claim 3, comprising common drive means for jointly driving said conveyors 5. A dryer according to claim 3, comprising independent drive means for each of said conveyors.

6. A dryer according to claim 1, comprising batchers positioned in said outlet means for said dried materials for drying loose and freely flowing materials. 

1. A convection dryer with a travelling bed, comprising; a pair of parallel spaced perforated walls; a movable conveyor extending between said walls in generally vertically and horizontally paths of movement; said conveyor including shelves and chain means interconnecting said shelves so as to define an enclosed chamber encompassed by said conveyor and said walls; inlet means for supplying wet materials to horizontal portions of said conveyor; outlet means for removing dried materials from horizontal portions of said conveyor; inlet means for supplying a gaseous drying medium into said enclosed chamber; and outlet means for withdrawing said drying medium, said inlet and outlet means for said gaseous drying medium being positioned so as to effect flow of said drying medium through said materials in at least the vertical portions of said movable conveyor.
 2. A dryer according to claim 1; comprising cascade sieve means being positioned in the outlet means for said dried materials, said cascade sieve means including outlets for withdrawing respectively fine and coarse fractions of said materials; oil spray means connected to at least one of said last-mentioned outlets; and ramming means positioned at the horizontal portions of said conveyor proximate said inlet means for said wet materials and being adapted to compact said materials.
 3. A dryer according to claim 1, comprising a pair of said conveyors each having triangular paths of movement including a vertical and an upper horizontal portion; inlet means for said wet materials communicating with the upper horizontal portions of each of said conveyors; and outlet means for said dried materials being located proximate the lower ends of said conveyors.
 4. A dryer according to claim 3, comprising common drive means for jointly driving said conveyors.
 5. A dryer according to claim 3, comprising independent drive means for each of said conveyors.
 6. A dryer according to claim 1, comprising batchers positioned in said outlet means for said dried materials for drying loose and freely flowing materials. 